With reference to FIG. 1 of the drawings, the dorsal side of the bone structure of a patient's left hand and wrist is illustrated in conjunction with the radius 2 and the ulna 4. The bone structure includes a carpal bone complex 6 having a scaphoid 8, a lunate 10, a triquetrum 12, a pisiform 14, a trapezium 16, a trapezoid 18, a capitate 20 and a hamate 22. It will be appreciated that the scaphoid 8 and the lunate 10 bones articulate with the radius 2 during the movement of the wrist.
In a variety of wrist disorders, patients may experience discomfort, pain and difficulty in moving the wrist. Prior surgical treatment of this condition involved fusion to inhibit movement of the scaphoid 8 and the lunate 10 bones relative to the radius to thereby alleviate pain in the patient's wrist. This procedure, however, leaves the patient without motion in their wrist and thereby severely restricts the use of their wrist. Prosthetic wrist implants have been developed to provide a pair of artificial bearing surfaces for the wrist. Several of the prior wrist implants have suffered from drawbacks including limited range of motion and excessive bone resection. Others still provide proper motion only when aligned in an extremely precise manner relative to the carpal bone complex 6. While various jigs and fixtures may be employed to aid in the locating and forming of a hole in the distal portion of the carpal bone complex 6 for receiving a carpal implant, these devices typically do not completely eliminate the possibility of error in the alignment and forming of the hole.
Accordingly, there remains a need in the art for an improved prosthetic wrist implant that provides improved support and strength for the distal portion of the carpal bone complex 6 and which has a bearing surface whose orientation is changeable after implantation to provide the implanted prosthetic wrist with a range of motion that mimics the range of motion of a natural wrist.